1. Field of the Invention
The present invention relates to a vehicular seat forming an automotive seat.
2. Description of the Related Art
Conventionally, a vehicle is provided with a seat 801 as shown in FIG. 7. The seat 801 is fixed to a floor 803 via a driving unit 802 for moving the seat 801 between the outside and inside of cabin (for example, see Japanese Patent Laid-Open No. 2001-001811).
The driving unit 802 includes a rotation mechanism 811 and a slide mechanism 812 provided on the rotation mechanism 811, and is constructed so as to be capable of moving the seat 801 to the outside of cabin after turning the seat 801 to the door opening side.
The slide mechanism 812 includes a pair of inner rails 822 formed on a swivel upper portion 821 turned by the rotation mechanism 811, a pair of center rails 823 provided on the outside of both the inner rails 822, and a pair of outer rails 824 provided on the outside of the center rails 823. The seat 801 is fixed to a seat leg 825 bridging the outer rails 824.
The swivel upper 821 is provided with a drive motor (not shown), and a driving chain 832 is set around a drive sprocket 831 rotated by the drive motor. The driving chain 832 is returned by a sprocket 833 at the rear end of the inner rail 822, and one end thereof is fixed to a center bracket 834 bridged to the rear end portion of the center rail 823. Also, the driving chain 832 is returned by a sprocket 835 at the front end of the inner rail 822, and the other end thereof is fixed to the center bracket 834 of the center rails 823.
By this configuration, a drive mechanism is formed which moves the center rails 823 forward and backward with respect to the inner rails 822 when the driving chain 832 is driven by the drive sprocket 831.
Also, one end of a return chain 841 is fixed to the swivel upper 821, and the return chain 841 is returned by a sprocket 842 at the rear end of the center rail 823. The other end of the return chain 841 is fixed to an outer bracket 843 bridged between the rear end portions of the outer rails 824.
By this configuration, a pullback mechanism is formed in which when the driving chain 832 is driven to pull back the center rails 823 to the proximal end side, the sprocket 842 at the rear end of the center rail 823 moves an intermediate portion of the return chain 841 to the proximal end side, so that the return chain 841 pulls back the outer rails 824. Thereby, the seat 801 supported on the outer rails 824 can be pulled back into the cabin.
However, for the vehicular seat as constructed above, when the outer rails 824 are extended to the outside of cabin, the extending movement inevitably relies on a lowering force due to gravitation along the inclined center rails 823.
Therefore, if the outer rails 824 are caught by something, the outer rails 824 cannot be extended smoothly, which hinders the movement of the seat 801.